This application claims the priority benefit of Taiwan application Ser. No. 90201456, filed Jan. 29, 2001.
1. Field of Invention
The present invention relates generally to an overvoltage protector. More particularly, the present invention relates to an overvoltage protector of a burn-in board.
2. Description of the Related Art
FIG. 1 is a circuit diagram of a conventional overvoltage protector of a burn-in board. The conventional overvoltage protector 10 utilizes a zener and a fuse to protect the circuit. When a value of a voltage Vin is higher than the value of the zener 12, the zener 12 will be damaged to cause a short circuit. At the same time, a high short circuit current flows into the zener 12 and the fuse 14, because the short circuit current is higher than a current limit of the fuse 14. Thus, the fuse will burn and break. Thus, no voltage will be able to flow through the circuit in order to protect the IC of the burn-in board from damage.
However, the conventional overvoltage protector can only be set at certain a voltage value, for example 3.3V or 5.1V. These values limit the utilization of the overvoltage protector. If 4.3V of output voltage Vo is transmitted through the circuit and the value is not the same as the set value, then the zener will not be able to perform its protection function. If a driving device that transmits the input voltage Vin is affected by some factors such as an unstable power transmission, the output voltage Vo also will be affected, which can lead to damage of the IC on the burn-in board.
If the conventional overvoltage protector is utilized in a laboratory, some experiments can cause the circuit to short easily, for example a high temperature operation life (HTOL) test, a low temperature operation life (LTOL) test, a high temperature bias life (HTBL) test, a temperature humidity bias (THB) test and a high accelerated stress test (HAST). The sudden short circuit can cause the experiments to repeat. Thus the reliability of the IC and the overvoltage protector is reduced.
It is an object of the present invention to provide an overvoltage protector of a burn-in board which can set a protecting voltage value according to the requirements of the design. The present invention ensures that the output voltage V, does not exceed the set protecting voltage value and prevents the IC and other components on the burn-in board from damage.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, the present invention provides a burn-in board of an overvoltage protector which has a voltage input that receives an input voltage and a voltage output that transmits out an output voltage. The voltage input and voltage output of the overvoltage protector both comprise a first end and a second end, wherein the second end of the voltage input is coupled to the second end of the voltage output. The overvoltage protector further comprises: a fuse that has a first end coupled to the first end of the voltage input and a second end coupled to the first end of the voltage output; a first storage device, which has a first end coupled to the first end of the voltage output and a second end coupled to the second end of the voltage output; a gate controlling switch, comprising a source, a drain and a gate, wherein the source is coupled to the first end of the voltage output and the drain is coupled to the second end of the voltage output; a resistor that has a first end coupled to the first end of the voltage output and a second end coupled to the gate control switch; and a second storage device that has a first end coupled to the first end of the voltage output and a second end coupled to the second end of the voltage output.
The present invention provides another burn-in board of an overvoltage protector, which has a voltage input that receives an input voltage and a voltage output that transmits an output voltage. The voltage input and voltage output of the overvoltage protector both comprise a first end and a second end, wherein the second end of the voltage input is coupled to the second end of the voltage output. The overvoltage protector further comprises: a breaker fuse that has a first end coupled to the first end of the voltage input and a second end coupled to the first end of the voltage output; a first capacitor, which has a first end coupled to the first end of the voltage output and a second end coupled to the second end of the voltage output; a gate controlling switch comprising a source, a drain and a gate, wherein the source is coupled to the first end of the voltage output and the drain is coupled to the second end of the voltage output; a resistor that has a first end coupled to the first end of the voltage output and a second end coupled to the gate control switch; and a second capacitor that has a first end coupledg to the first end of the voltage output and a second end of the second capacitor coupled to the second end of the voltage output.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.